Process for forming image with liquid droplets, image forming apparatus utilizing such process and process for ejecting and projecting liquid droplets

Abstract

An image forming process provides an excellent ink fixation effect for high speed, low energy consumption printing. Two-valued or multi-valued gradation expression of a picture element, or the smallest output unit, is realized by controlling the number of liquid droplets impacting on a recording medium for each dot formed on the recording medium. The liquid droplets are subjected to physical or chemical modification so as to be fixed to the recording medium. The present invention is also directed to an image forming apparatus, an ink for liquid droplet recording and a liquid droplet ejection and projection method that can use the image forming process.

1. An image forming process for forming an image on a recording medium with dots of ink, comprising the steps of:
 generating the ink droplets such that each ink dot fixed on the recording medium has an average equivalent circle diameter of 10 μm or less; and  
 fixing the ink to the recording medium by physical or chemical modification,  
 wherein the ink droplets are formed from an ink containing block polymers having a polyvinyl ether structure,  
 wherein the polyvinyl ether structure has a repeating unit structure expressed by the following general formula: 
                 
 
 
       where 1 represents an integer of 1 to 18, each of R 2  and R 3  is independently either H or CH 3  and R 4  is selected from hydrogen, a straight chain, branched or cyclic alkyl group with 1 to 18 carbon atoms, and
 wherein at least one block of the block polymers has a stimuli responsive property and by the stimuli the ink is modified from a state of low viscosity to a state of high viscosity.  
 
     
     
       2. The image forming process according to  claim 1 , wherein
 multi-valued gradation expression of a picture element, which is a smallest unit for output, is performed by controlling the number of ink droplets impacting on the recording medium to form each dot.  
 
     
     
       3. The image forming process according to  claim 1 , wherein
 ink droplets of two or more different types are used and subjected to the physical or chemical modification when the ink droplets of different types are brought into contact with each other.  
 
     
     
       4. The image forming process according to  claim 1 , wherein
 the ink shows thermal sol-gel transition.  
 
     
     
       5. The image forming process according to  claim 1 , wherein
 the ink droplets are formed from an ink containing a silicon compound or a fluorine compound having a reactive group.  
 
     
     
       6. The image forming process according to  claim 1 , wherein
 the ink droplets are formed from an ink having a reactive property, and wherein a process of transition from sol containing a silicon oxide or a metal oxide to gel is performed.  
 
     
     
       7. The image forming process according to  claim 1 , wherein the ink droplets are formed from an aqueous dispersion ink having a stimuli responsive property and containing a polymer having a polyvinylether structure, water and a pigment or dye. 
     
     
       8. The image forming process according to  claim 7 , wherein
 the stimuli responsive property is a property of changing the state of the ink in response to a temperature change or an electromagnetic wave.  
 
     
     
       9. The image forming process according to  claim 7 , wherein
 the stimuli responsive property is a property of changing the state of the ink in response to a pH change or an ink density change.  
 
     
     
       10. The image forming process according to  claim 1 , wherein
 the ink further has a block polymer having a repeating unit structure expressed by the following general formula: 
   —(CH 2 —CH (OR 1 ))—,  
 
 where R 1  is selected from a straight chain, branched or cyclic alkyl group with 1 to 18 carbon atoms, Ph, pyridyl (Pyr), Ph-Ph, Ph-Pyr, or —(CH(R 2 )—CH (R 3 )—O) 1 —R 4  or —(CH 2 ) m —(O) m —R 4 , the hydrogen in the aromatic ring can be substituted by a straight chain or branched alkyl group with 1 to 4 carbon atoms, while the carbon in the aromatic ring can be substituted by nitrogen, 1 represents an integer between 1 and 18 and m represents an integer between 1 and 36, while n represents 0 or 1, each of R 2  and R 3  is independently either H or CH 3  and R 4  is selected from hydrogen, a straight chain, branched or cyclic alkyl group with 1 to 18 carbon atoms, Ph, Pyr, Ph-Ph, Ph-Pyr, —CHO, —CO—CH═CH 2  and —CO—C(CH 3 )═CH 2 , if the R 4  group is other than hydrogen, the hydrogen bonded to each carbon atom of R 4  can be substituted by a straight chain or branched alkyl group with 1 to 4 carbon atoms, F, Cl or Br and the carbon in the aromatic ring can be substituted by nitrogen.  
 
     
     
       11. The image forming process according to  claim 1 , wherein
 the image is formed by developing a latent image thereof by means of the ink droplets.  
 
     
     
       12. The image forming process according to  claim 1 , wherein
 the image is formed by transferring the ink droplets onto the recording medium by way of an intermediary transfer medium.  
 
     
     
       13. A process for ejecting ink droplets from an ejection head to a recording medium, comprising the steps of:
 ejecting the ink droplets such that each ink dot fixed on the recording medium has an average equivalent circle diameter of 10 μm or less; and  
 fixing the ink to the recording medium by physical or chemical modification,  
 wherein the ink droplets are formed from an ink containing block polymers having a polyvinyl ether structure,  
 wherein the polyvinyl ether structure has a repeating unit structure expressed by the following general formula: 
                 
 
 where 1 represents an integer of 1 to 18, each of R 2  and R 3  is independently either H or CH 3  and R 4  is selected from hydrogen, a straight chain, branched or cyclic alkyl group with 1 to 18 carbon atoms, and  
 wherein at least one block of the block polymers has a stimuli responsive property and by the stimuli the ink is modified from a state of low viscosity to a state of high viscosity.  
 
     
     
       14. The process according to  claim 13 , wherein
 multi-valued gradation expression of a smallest unit for information output or input is realized by controlling the number of ink droplets impacting on the recording medium for each of the dots.  
 
     
     
       15. An image forming apparatus comprising ink ejection means for ejecting ink droplets such that each ink dot fixed on a recording medium has an equivalent circle diameter of 10 μm or less, and recording medium conveying means, the ink being fixed to the recording medium by physical modification or chemical modification,
 wherein the ink droplets are formed from an ink containing block polymers having a polyvinyl ether structure,  
 wherein the polyvinyl ether structure has a repeating unit structure expressed by the following general formula: 
                 
 
 where 1 represents an integer of 1 to 18, each of R 2  and R 3  is independently either H or CH 3  and R 4  is selected from hydrogen, a straight chain, branched or cyclic alkyl group with 1 to 18 carbon atoms, and  
 wherein at least one block of the block polymers has a stimuli responsive property and by the stimuli the ink is modified from a state of low viscosity to a state of high viscosity.  
 
     
     
       16. The image forming apparatus according to  claim 15 , wherein
 ink droplets of two or more different types are used and subjected to the physical or chemical modification when the ink droplets of different types are brought into contact with each other.